This invention relates generally to fuel filter systems employed in connection with internal combustion engines. More particularly, the present invention relates to fuel filter systems for removing foreign particles and separating water from the fuel supply or oil system of an internal combustion engine.
The absence of high standards of quality control in diesel fuel supplies dictates that an effective fuel filter be incorporated into the fuel supply system for a diesel engine. It is not uncommon for diesel fuel to have significant quantities of abrasive particles and water. The abrasive particles present the potential for permanent damage to components of the fuel injection pump. The abrasive particles can also adversely effect the performance of the pump by destroying the ability of the fuel injection pump to precisely meter and deliver fuel at high pressures. The presence of water in the diesel fuel supply can cause rusting of engine components, and during freezing conditions, can result in interruption of the fuel injection system and/or seizure of moving components.
A number of conventional fuel filters perform the dual function of removing particulate material from the diesel fuel and separating water from the fuel. Commonly, such fuel filters employ a disposable filter cartridge which is replaced at pre-established intervals of filter usage. Typically, a disposable filter/water separator cartridge is releasably secured to a base. A multi-stage filter assembly within the cartridge includes filtering and coalescing media and separates an upper portion of the chamber from a lower portion which functions as a water collection sump. The fuel filter may also feature a sensing device in the base to indicate the presence of a predetermined quantity of water in the sump. A petcock allows the water to be removed from the sump.
Briefly stated, the invention in a preferred form is a fuel filter system for removing foreign particles and separating water from the fuel supply of an internal combustion engine. The fuel filter system includes a first filter having a filter element that separates water from the fuel. The water collects in a sump in the lower portion of the first filter and exits the sump via an outlet. A second filter includes an enclosure having an inlet in fluid communication with the outlet of the first filter and an outlet in fluid communication with the fuel tank. A filter element composed of a hygroscopic material is contained in the enclosure. The water is absorbed by the hygroscopic material and any fuel that is entrained in the water is returned to the fuel tank via a return line.
The volume of the hygroscopic material increases as it absorbs water, restricting flow through the second filter and increasing the pressure inside the second filter and the waste line connecting the first and second filters. A pressure sensor monitors the pressure inside the second filter and sends a signal when the pressure reaches a predetermined level, indicating that the second filter must be changed. A pressure relief valve in the waste line has a setpoint below the first filter nominal pressure and above the signal pressure, thereby ensuring that there is no back flow from the second filter.
An object of the invention is to provide a new and improved fuel filter system.
Another object of the invention is to provide a new and improved fuel filter system having apparatus that facilitates disposal of water that is separated from the fuel.
A further object of the invention is to provide a new and improved fuel filter system having apparatus that reduces the cost of disposing water that is separated from the fuel.
Other objects and advantages of the invention will become apparent from the drawings and specification.